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The following Telemedicine takeaways are presented: telemedicine needs and limitations, communication system fundamentals, basics of satellite communications, and advancements in SatCom and 5G.
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Snow water equivalent (SWE) distribution at fine spatial scales (≤10 m) is difficult to estimate due to modeling and observational constraints. However, the distribution of SWE throughout the spring snowmelt season is often correlated to the timing of snow disappearance. Here, we show that snow cover maps generated from PlanetScope's constellation of Dove Satellites can resolve the 3 m date of snow disappearance across seven alpine domains in California and Colorado. Across a 5-year period (2019–2023), the average uncertainty in the date of snow disappearance, or the period of time between the last date of observed snow cover and the first date of observed snow absence, was 3 days. Using a simple shortwave-based snowmelt model calibrated at nearby snow pillows, the PlanetScope date of snow disappearance could be used to reconstruct spring SWE. Relative to lidar SWE estimates, the SWE reconstruction had a spatial coefficient of correlation of 0.75, and SWE spatial variability that was biased by 9%, on average. SWE reconstruction biases were then improved to within 0.04 m, on average, by calibrating snowmelt rates to track the spring temporal evolution of fractional snow cover observed by PlanetScope, including fractional snow cover over the full modeling domain, and across domain subsections where snowmelt rates may differ. This study demonstrates the utility of fine-scale and high-frequency optical observations of snow cover, and the simple and annually repeatable connections between snow cover and spring snow water resources in regions with seasonal snowpack.
A document containing a forecast of satellite traffic and revelant technology trends to the year 2000 was prepared which includes those space station capabilities and characteristics that should be provided to make the station useful to commercial satellite owners. The document was circulated to key representative organizations within the commercial telecommunications satellite and related communities of interest, including spacecraft manufacturers, commercial satellite owners, communications carriers, networks and risk insurers. The prospectus document is presented as well as the transmittal letter and the mailing list of the people and companies that were asked to review it. Key commercial telecommunications comments are summarized the actual response letters from the industry are included.
Based on a comprehensive evaluation of the fundamental Intersatellite Link (ISL) systems characteristics, potential applications of ISLs to domestic, regional, and global commercial satellite communications were identified, and their cost-effectiveness and other systems benefits quantified wherever possible. Implementation scenarios for the cost-effective communications satellite systems employing ISLs were developed for the first launch in 1993 to 1994 and widespread use of ISLs in the early 2000's. Critical technology requirements for both the microwave (60 GHz) and optical (0.85 micron) ISL implementations were identified, and their technology development programs, including schedule and cost estimates, were derived.
Personnel from the Goddard Space Flight Center Wallops Flight Facility (GSFC/WFF in Virginia have successfully tested commercial LEO communications satellites for sounding rocket, balloon and aircraft flight TT&C. The Flight Modern became a GSFC/WFF Advanced Range Technology Initiative (ARTI) in an effort to streamline TT&C capability to the user community at low cost. Ground tests of the Flight Modem verified duplex communications quality of service and measured transmission latencies. These tests were completed last year and results reported in the John Hopkins University (JHU) Applied Physics Laboratory (APL) 4th International Symposium on Reducing Spacecraft Costs for Ground Systems and Operations. The second phase of the Flight Modem baseline test program was a demonstration of the ruggedized version of the WFF Flight Modem flown on a sounding rocket launched it the Swedish rocket range (Esrangc) near Kiruna, Sweden, with results contained in this paper. Aircraft flight tests have been and continue to be conducted. Flights of opportunity are being actively pursued with other centers, ranges and users at universities. The WFF Flight Modem contains a CPS receiver to provide vehicle position for tracking and vehicle recovery. The system architecture, which integrates antennas, CPS receiver, commercial satellite packet data modem and a single board computer with custom software, is described. Small satellite use of the WFF Flight Modem is also being investigated, The Flight Modem provides an independent vehicle position source for Range Safety applications. The LEO communication system contains a coarse position location system, which is compared to GPS ace acy. This comparison allows users, to determine the need for a CPS receiver in addition to the satellite packet data modem for their application.
A Mobile Satellite Experiment (MSAT-X) is described, based on a planned cooperative U.S./Canadian program. The experiment would establish network architecture, develop system and ground-segment technology, and define the technical characteristics needed to help structure the regulatory/institutional framework needed to enable a first-generation commercial satellite service. A satellite of this type would augment terrestrial systems, both cellular and noncellular, in the thin-route/rural areas of the country where service is either unavailable or inadequate. Applications range from wide-area radio/dispatch (e.g., oil exploration and interstate trucking) to extension of the public mobile telephone service. Market estimates are provided and experiment objectives and requirements are delineated. The requirements are being developed in close coordination with the Department of Communications (DOC) of Canada and with industry and potential-user organizations. The paper closes with a development plan and milestone chart.
NASA spacecraft performing scientific and exploration missions may increasingly communicate over commercial relay satellites, including those that operate at Ka-band. Ideally these spacecraft could use the same Ka-band terminal for low-rate telemetry/commanding. However, this use case presents an issue since most commercial relay systems were designed with terrestrial users in mind and cannot easily handle the Doppler effects of orbiting spacecraft. In this work we propose onboard Doppler compensation allowing spacecraft to use existing relay satellite infrastructure without modification. Specifically, we present a method for digital compensation based on a series of piecewise linear sweeps which minimizes resources used on the spacecraft’s radio. We perform orbital mechanics simulations to estimate the worst-case Doppler profiles experienced by spacecraft in several low-Earth orbits. We emulate these effects in a laboratory experiment and demonstrate the proposed technique will reduce Doppler effects by more than two orders of magnitude. The residual Doppler is small enough that modems used at commercial relay sites are able to receive error-free data even when operating at their lowest supported symbol rate.
As part of NASA's Integrated Operations Architecture (IOA) Baseline, NASA will consolidate all communications operations. including ground-based, near-earth, and deep-space communications, into a single integrated network. This network will make maximum use of commercial equipment, services and standards. It will be an Internet Protocol (IP) based network. This study supports technology development planning for the IOA. The technical problems that may arise when LEO mission spacecraft interoperate with commercial satellite services were investigated. Commercial technology and services that could support the IOA were surveyed, and gaps in the capability of existing technology and techniques were identified. Recommendations were made on which gaps should be closed by means of NASA research and development funding. Several findings emerged from the interoperability assessment: in the NASA mission set, there is a preponderance of small. inexpensive, low data rate science missions; proposed commercial satellite communications services could potentially provide TDRSS-like data relay functions; and. IP and related protocols, such as TCP, require augmentation to operate in the mobile networking environment required by the space-to-ground portion of the IOA. Five case studies were performed in the technology assessment. Each case represented a realistic implementation of the near-earth portion of the IOA. The cases included the use of frequencies at L-band, Ka-band and the optical spectrum. The cases also represented both space relay architectures and direct-to-ground architectures. Some of the main recommendations resulting from the case studies are: select an architecture for the LEO/MEO communications network; pursue the development of a Ka-band space-qualified transmitter (and possibly a receiver), and a low-cost Ka-band ground terminal for a direct-to-ground network, pursue the development of an Inmarsat (L-band) space-qualified transceiver to implement a global, low data rate network for LEO/MEO, mission spacecraft; and, pursue developmental research for a miniaturized, high data rate optical transceiver.
Results are presented for the technical experiments conducted by the U.S. Maritime Administration (MARAD) using the ATS-6 satellite operating in the L-band fan beam mode. The MARAD experiments were conducted with satellite terminals placed on two commercial ships for evaluation of the communication service similar to that which will be available with a maritime commercial satellite system. Evaluation of position determination with a satellite was also made. Three modems having voice and digital data and a stabilized shipboard L-band antenna system were assessed. The ship antenna demonstrated successful tracking of the satellites for test period intervals of 4 to 6 hr without the need for operator adjustment. The ship position determination tests showed good measurement repeatability. The data analyzed supported the ability of future commercial satellite systems to achieve a probability of bit error of better than 0.00001.
The economic and financial aspects of newly defined space-based activities, procedures, and operations (APOs) and associated satellite system designs are presented that have the potential to improve economic performance of future geostationary communications satellites. Launch insurance, launch costs, and the economics of APOs are examined. Retrieval missions and various Space Station scenarios are addressed. The potential benefits of the new APOs to the commercial communications satellite system operator are quantified.
The NASA Space Communications and Navigation (SCaN) Program is responsible for providing communication and navigation services to scientific and human space exploration missions. SCaN's current Space Network provides radio frequency (RF) relay services to near Earth space missions via Tracking and Data Relay Satellites (TDRS). SCaN plans to offer a new generation of relay services beginning in 2025, including the addition of optical communications capabilities and enhanced RF capabilities. The primary drivers behind the development of these next generation relay network services are to enhance communication and navigation services with significantly reduced development and operational costs. Several approaches being considered for implementation of these services are through government owned capabilities, through commercial service providers, or a combination of the two. One approach receiving a great deal of attention is the use of Public-Private Partnerships (PPP) to develop and provide capabilities or services. Utilizing Public-Private Partnerships allows NASA and commercial entities to share the investment, standards, and risks of developing and testing new or enhanced capabilities which can benefit both NASA and the commercial space communication industry. The capabilities developed under the PPP can then be used to support the growth of the commercial satellite communications industry while simultaneously being introduced into NASA operations to provide service to future NASA missions as part of the NASA Next Generation Architecture. Partnerships formed for this purpose can also serve as the basis for further NASA acquisition activities where government and industry can continue to share the cost, risk, and benefits of space communications capability development and operations. This objective is consistent with the 2010 National Space Policy stated principles: "The United States is committed to encouraging and facilitating the growth of a U.S. commercial space sector that supports U.S. needs, is globally competitive, and advances U.S. leadership in the generation of new markets and innovation-driven entrepreneurship." [1]NASA has conducted several internal studies as well as externally funded studies with industry to define the next generation space communication architecture. NASA has approached the commercial industry through a Request for Information (RFI) to define further the next generation architecture and has conducted numerous internal and external studies. The results are promising and are shaping the approach to utilize Public Private Partnership to achieve NASA's objectives while reducing costs. The commercial satellite industry has begun to deploy high performance, high throughput global satellite constellations which have the potential to provide communication services to NASA Missions. Commercial satellite manufacturers have advanced their processes to rapidly design, build, and deliver, reliable communication satellites using minimum government oversight. In this paper, we will 1) describe the NASA Next Generation Architecture, Concept of Operations (ConOps), and salient characteristics; 2) Discuss the rational of Public-Private Partnerships to achieve NASA’s next generation communication architecture; and 3) Summarize the preliminary analysis performed to date and describe the path forward.
Only eight years after the launc of Sputnik-1 by the Soviet Union, the first commercial satellite, 'Early Bird', entered service. In just twelve years commercial satellite service extended around the earth and became profitable. The reasons for the successful development of the communications satellite services in a comparatively short time are considered. These reasons are related to the presence of three ingredients, taking into account technology to create the system, communications requirements to form a market, and a management structure to implement the system. The formation of the concept of using earth orbiting satellites for telecommunications is discussed. It is pointed out that the years from 1958 to 1964 were the true 'experimental years' for satellite communications. The rapid development of technology during this crucial period is described, giving attention to passive satellites, active systems, and development satellites.
Various issues associated with assessing emerging networks to support future NASA space operations are presented in viewgraph form. Specific topics include: 1) Emerging commercial satellite systems; 2) NASA LEO satellite support through commercial systems; 3) Communications coverage, user terminal assessment and regulatory assessment; 4) NASA LEO missions overview; and 5) Simulation assumptions and results.
Utilizing commercial or military satellites as testbeds for subsystems is a potential platform for small devices. Electric propulsion is a viable and upcoming subsystem that is of high interest to planetary mission engineers as well as commercial satellite developers. It is proposed that by incorporating small lightweight electric propulsion devices onto small satellites as external or 'bolt-on' experiments, an increase in the number of flight opportunities can occur. Specific problems are spacecraft body interaction, contamination effects, thermal interface problems, power conditioning control electronics, and propulsion feed system interfaces.